Tumor necrosis factor (TNF or TNF-α) and lymphotoxin (LT or TNF-β) are related cytokines that share 40 percent amino acid (AA) sequence homology. Old (1987) Nature 330:602-603. These cytokines are released mainly by macrophages, monocytes and natural killer (NK) cells in response to broad immune reactions. Gorton and Galli (1990) Nature 346:274-276; and Dubravec et al. (1990) Proc. Natl. Acad. Sci. USA 87:6758-6761. Although initially discovered as agents inducing hemorrhagic necrosis of tumors, these cytokines have been shown to have essential roles in both the inductive and effector phases of immune reactions and inflammation. The two cytokines cause a broad spectrum of effects on cells in vitro and tissues in vivo, including: (i) vascular thrombosis and tumor necrosis; (ii) inflammation; (iii) activation of macrophages and neutrophils; (iv) leukocytosis; (v) apoptosis; and (vi) shock. Beretz et al. (1990) Biorheology 27:455-460; Driscoll (1994) Exp. Lung Res. 20:473-490; Ferrante (1992) Immunol. Ser. 57:417-436; Golstein et al. (1991) Immunol. Rev. 121:29-65; and van der Poll and Lowry (1995) Shock 3:1-12. For a review of the mechanism of action of TNF, see Massague (1996) Cell 85:947-950. TNF has been associated with a variety of disease states including various forms of cancer, arthritis, psoriasis, endotoxic shock, sepsis, autoimmune diseases, infections, obesity, and cachexia. Attempts have been made to alter the course of a disease by treating the patient with TNF inhibitors with varying degrees of success. For example, oxpentifylline did not alter the course of Crohn's disease, a chronic inflammatory bowel disease. Bauditz et al. (1997) Gut 40:470-4. However, the TNF inhibitor dexanabinol provided protection against TNF following traumatic brain injury. Shohami et al. (1997) J. Neuroimmun. 72:169-77.
Human TNF and LT mediate their biological activities, both on cells and tissues, by binding specifically to two distinct, although related, glycoprotein plasma membrane receptors of 55 kDa and 75 kDa (p55 and p75 TNF-R, respectively). Holtmann and Wallach (1987) J. Immunol. 139:151-153. The two receptors share 28 percent AA sequence homology in their extracellular domains, which are composed of four repeating cysteine-rich regions. Tartaglia and Goeddel (1992) Immunol. Today 13:151-153. However, the receptors lack significant AA sequence homology in their intracellular domains. Dembic et al. (1990) Cytokine 2:231-237. Due to this dissimilarity, they may transduce different signals and, in turn, exercise diverse functions.
Recent studies have shown that most of the known cellular TNF responses, including cytotoxicity and induction of several genes, may be attributed to p55 TNF-R activation. Engelmann et al. (1990) J. Biol. Chem. 265:1531-1536; Shalaby et al. (1990) J. Exp. Med. 172:1517-1520; and Tartaglia et al. (1991) Proc. Natl. Acad. Sci. USA 88:9292-9296. In addition, the p55 receptor controls early acute graft-versus-host disease. Speiser et al. (1997) J. Immun. 158:5185-90. In contrast, information regarding the biological activities of p75 TNF-R is limited. This receptor shares some activities with p55 TNF-R and specifically participates in regulating proliferation of and secretion of cytokines by T cells. Shalaby et al. (1990); and Gehr et al. (1992) J. Immunol. 149:911-917. Both belong to an ever-increasing family of membrane receptors including low-affinity nerve growth factor receptor (LNGF-R), FAS antigen, CD27, CD30 (Ki-1), CD40 (gp50) and OX 40. Cosman (1994) Stem Cells (Dayt.) 12:440-455; Meakin and Shooter (1992) Trends Neurosci. 15:323-331; Grell et al. (1994) Euro. J. Immunol. 24:2563-2566; Moller et al. (1994) Int. J. Cancer 57:371-377; Hintzen et al. (1994) J. Immunol. 152:1762-1773; Smith et al. (1993) Cell 73:1349-1360; Corcoran et al. (1994) Eur. J. Biochem. 223:831-840; and Baum et al. (1994) EMBO J. 13:3992-4001.
All of these receptors share a repetitive pattern of cysteine-rich domains in their extracellular regions. In accord with the pleiotropic activities of TNF and LT, most human cells express low levels (2,000 to 10,000 receptors/cell) of both TNF-Rs simultaneously. Brockhaus et al. (1990) Proc. Natl. Acad. Sci USA 87:3127-3131. Expression of TNF-R on both lymphoid and non-lymphoid cells may be up and down-regulated by many different agents, such as bacterial lipopolysaccharide (LPS), phorbol myristate acetate (PMA; a protein kinase C activator), interleukin-1 (IL-1), interferon-gamma (IFN-γ) and IL-2. Gatanaga et al. (1991) Cell Immunol. 138:1-10; Yui et al. (1994) Placenta 15:819-835; and Dett et al. (1991) J. Immunol. 146:1522-1526. Although expressed in different proportions, each receptor binds TNF and LT with equally high affinity. Brockhaus et al. (1990); and Loetscher et al. (1990) J. Biol. Chem. 265:20131-20138. Initial studies showed that the complexes of human TNF and TNF-R are formed on the cell membrane, internalized wholly, and then either degraded or recycled. Armitage (1994) Curr. Opin. Immunol. 6:407-413; and Fiers (1991) FEBS Lett. 285:199-212.
TNF binding proteins (TNF-BP) were originally identified in the serum and urine of febrile patients, individuals with renal failure, cancer patients, and even certain healthy individuals. Seckinger et al. (1988) J. Exp. Med. 167:1511-1516; Engelmann et al. (1989) J. Biol. Chem. 264:11974-11980; Seckinger et al. (1989) J. Biol. Chem. 264:11966-11973; Peetre et al. (1988) Eur. J. Haematol. 41:414-419; Olsson et al. (1989) Eur. J. Haematol. 42:270-275; Gatanaga et al. (1990a) Lymphokine Res. 9:225-229; and Gatanaga et al. (1990b) Proc. Natl. Acad. Sci USA 87:8781-8784. In fact, human brain and ovarian tumors produced high serum levels of TNF-BP. Gatanaga et al. (1990a); and Gatanaga et al. (1990b). These molecules were subsequently purified, characterized, and cloned by different laboratories. Gatanaga et al. (1990b); Olsson et al. (1989); Schall et al. (1990) Cell 61:361-370; Nophar et al. (1990) EMBO J. 9:3269-3278; Himmler et al. (1990) DNA Cell Biol. 9:705-715; Loetscher et al. (1990) Cell 61:351-359; and Smith et al. (1990) Science 248:1019-1023. These proteins have been suggested for use in treating endotoxic shock. Mohler et al. (1993) J. Immunol. 151:1548-1561; Porat et al. (1995) Crit. Care Med. 23:1080-1089; Fisher et al. (1996) N. Engl. J. Med. 334:1697-1702; Fenner (1995) Z. Rheumatol. 54:158-164; and Jin et al. (1994) J. Infect. Dis. 170:1323-1326.
Human TNF-BP consist of 30 kDa and 40 kDa proteins found to be identical to the N-terminal extracellular domains of p55 and p75 TNF-R, respectively. The 30 kDa and 40 kDa TNF-BP are thus also termed soluble p55 and p75 TNF-R, respectively. Studies of these proteins have been facilitated by the availability of human recombinant 30 kDa and 40 kDa TNF-BP and antibodies which specifically recognize each form and allow quantitation by immunoassay. Heller et al. (1990) Proc. Natl. Acad. Sci. USA 87:6151-6155; U.S. Pat. No. 5,395,760; EP 418,014; and Grosen et al. (1993) Gynecol. Oncol. 50:68-77. X-ray structural studies have demonstrated that a TNF trimer binds with three soluble TNF-R (sTNF-R) molecules and the complex can no longer interact with TNF-R. Banner et al. (1993) Cell 73:431-445. The binding of the trimer and sTNF-R, however, is reversible and these reactants are not altered as a result of complex formation. At high molar ratios of sTNF-R to TNF, both recombinant and native human sTNF-R are potent inhibitors of TNF/LT biological activity in vitro as well as in vivo. Gatanaga et al. (1990b); Ashkenazi et al. (1991) Proc. Natl. Acad. Sci. USA 88:10535-10539; Lesslaur et al. (1991) Eur. J. Immunol. 21:2883-2886; Olsson et al. (1992) Eur. J. Haematol. 48:1-9; and Kohno et al. (1990) Proc. Natl. Acad Sci. USA 87:8331-8335.
Increased levels of TNF-R are also associated with clinical sepsis (septic peritonitis), HIV-1 infection, and other inflammatory conditions. Kalinkovich et al. (1995) J. Interferon and Cyto. Res. 15:749-757; Calvano et al. (1996) Arch. Surg. 131:434-437; and Ertel et al. (1994) Arch. Surg. 129:1330-1337. Sepsis, and septic shock affect thousands of patients every year and there is essentially no cure. This lethal syndrome is caused primarily by lipopolysaccharides (LPS) of Gram-negative bacteria and superantigens of Gram-positive bacteria. Clinical symptoms are initiated primarily by the release of endogenous mediators, such as TNF, from activated lymphoid cells into the bloodstream. TNF induces production of a cascade of other cytokines, including IL-1, gamma-Interferon, IL-8, and IL-6. These cytokines, along with other factors, promote the clinical symptoms of shock. Recombinant human sTNF-R is currently being tested in clinical trials to block TNF/LT activity in patients with septic shock and other conditions in which TNF and LT are thought to be pathogenic. Van Zee et al. (1992) Proc. Natl. Acad. Sci. USA 89:4845-4849. Balb/c mice, the primary animal model, and multiple techniques have been used to test the effects of TNF modulators and other treatments on septic peritonitis. Jin et al. (1994) J. Infect. Dis. 170:1323-1326; Mohler et al. (1993) J. Immunol. 151:1548-1561; Porat et al. (1995) Crit. Care Med. 23:1080-1089; and Echtenacher et al. (1996) Nature 381:75-77. Lipopolysaccharide-induced shock has been shown to be ameliorated by FR167653, a dual inhibitor of IL-1 and TNF production. Yamamoto et al. (1997) Eur. J. Pharmacol. 327:169-174.
Attempts have been made to ameliorate the untoward effects of TNF by treatment with monoclonal antibodies to TNF or with other proteins that bind TNF, such as modified TNF receptors. Patients with sepsis or septic shock were treated with anti-TNF antibodies. Salat et al. (1997) Shock 6:233-7. Some improvement in the clinical and histopathologic signs of Crohn's disease were afforded by treatment with anti-TNF antibodies. Neurath et al. (1997) Eur. J. Immun. 27:1743-50; van Deventer et al. (1997) Pharm. World Sci. 19:55-9; van Hogezand et al. (1997) Scand. J. Gastro. 223:105-7; and Stack et al. (1997) Lancet 349:521-4. In the treatment of experimental autoimmune encephalitis (EAE), an animal model of the human disease multiple sclerosis (MS), treatment with TNF-R fusion protein prevents the disease and the accompanying demyelination, suggesting the possible use of this treatment in MS patients. Klinkert et al. (1997) J. Neuroimmun. 72:163-8. Neither coagulation nor the fibrinolytic system was affected by an anti-TNF antibody in a study of patients with sepsis or septic shock. Satal et al. (1996) Shock 6:233-7.
Regulation of TNF expression is being tested in treatment of endotoxic shock. Mohler et al. (1994) Nature 370:218-220. Modulation of TNF-R activity is also being approached by the use of peptides that bind intracellularly to the receptor or other component in the process to prevent receptor shedding. PCT patent publications: WO 95/31544, WO 95/33051; and WO 96/01642. Modulation of TNF-R activity is also postulated to be possible by binding of peptides to the TNF-R and interfering with signal transduction induced by TNF. European Patent Application EP 568 925.
While low levels of sTNF-R have been identified in the sera of normal individuals, high levels have been found in the sera of patients with chronic inflammation, infection, renal failure and various forms of cancer. Aderka et al. (1992) Lymphokine Cytokine Res. 11:157-159; Olsson et al. (1993) Eur. Cytokine Netw. 4:169-180; Diez-Ruiz et al. (1995) Eur. J. Haematol. 54:1-8; van Deuren (1994) Eur. J. Clin. Microbiol. Infect. Dis. 13 Suppl. 1:S12-6; Lambert et al. (1994) Nephrol. Dial. Transplant. 9:1791-1796; Halwachs et al. (1994) Clin. Investig. 72:473-476; Gatanaga et al. (1990a); and Gatanaga et al. (1990b). Serum levels of sTNF-R rise within minutes and remain high for 7 to 8 hours after the intravenous injection of human recombinant TNF or IL-2 into human cancer patients. Aderka et al. (1991) Cancer Res. 51:5602-5607; and Miles et al. (1992) Br. J. Cancer 66:1195-1199. Contrarily, serum sTNF-R levels are chronically elevated in cancer patients and may remain at high levels for years. Grosen et al. (1993). It is clear that sTNF-R are natural inhibitors of these cytokines and regulate their biological activity post secretion. Fusion proteins consisting of a sTNF-R linked to a portion of the human IgG1 have also been developed for treating rheumatoid arthritis and septic shock. Moreland et al. (1997) N. Eng. J. Med. 337:141-7; Abraham et al. (1997) JAMA 277:1531-8.
New evidence has yielded information on cellular regulation of secreted cytokines. The evidence indicates that cells release molecules which resemble or contain the binding site of the specific membrane receptors. Massague and Pandiella (1993) Annul. Rev. Biochem. 62:515-541; and Rose John and Heinrich (1994) Biochem. J. 300:281-290. These soluble forms specifically bind and, in the appropriate molar ratios, inactivate the cytokine by steric inhibition. Therefore, this may be a general phenomenon responsible for the regulation of cytokines and membrane antigens.
Notably, in addition to TNF-R, various types of membrane molecules have both soluble and membrane forms, including (i) cytokine receptors, e.g., IL-1R, IL-2R, IL-4R, IL-5R, IL-6R, IL-7R, IL-9R, granulocyte-colony stimulating factor-R (G-CSF-R), granulocyte-macrophage-colony stimulating factor-R (GM-CSF-R), transforming growth factor-β-R (TGFβ-R), platelet-derived growth factor-R (PDGF-R), and epidermal growth factor-R (EGF-R); (ii) growth factors, e.g., TNF-(pro-TNF-α), TGF-α, and CSF-1; (iii) adhesion molecules, e.g., intracellular adhesion molecule-1 (ICAM-1/CD54) and vascular cell membrane adhesion molecule (VCAM-1/CD106); (iv) TNF-R/NGF-R superfamily, e.g., LNGF-R, CD27, CD30, and CD40; and (v) other membrane proteins, e.g. transferrin receptor, CD14 (receptor for LPS and LPS binding protein), CD16 (FcγRIII), and CD23 (low-affinity receptor for IgE). Colotta et al. (1993) Science 261:472-475; Baran et al. (1988) J. Immunol. 141:539-546; Mosley et al. (1989) Cell 59:335-348; Takaki et al. (1990) EMBO J. 9:4367-4374; Novick et al. (1989) J. Exp. Med. 170:1409-1414; Goodwin et al. (1990) Cell 60:941-951; Renauld et al. (1992) Proc. Natl. Acad. Sci. USA 89:5690-5694; Fukunaga et al. (1990) Proc. Natl. Acad. Sci. USA 87:8702-8706; Raines et al. (1991) Proc. Natl. Acad. Sci. USA 88:8203-8207; Lopez-Casillas et al. (1991) Cell 67:785-795; Tiesman and Hart (1993) J. Biol. Chem. 268:9621-9628; Khire et al. (1990) Febs. Lett. 272:69-72; Kriegler et al. (1988) Cell 53:45-53; Pandiella and Massague (1991) Proc. Natl. Acad. Sci. USA 88:1726-1730; Stein et al. (1991) Oncogene 6:601-605; Seth et al. (1991) Lancet 338:83-84; Hahne et al. (1994) Eur. J. Immunol. 24:421-428; Zupan et al. (1989) J. Biol. Chem. 264:11714-11720; Loenen et al. (1992) Eur. J. Immunol. 22:447-455; Latza et al. (1995) Am. J. Pathol. 146:463-471; Chitambar (1991) Blood 78:2444-2450; Landmann et al. (1992) J. Leukoc. Biol. 52:323-330; Huizinga et al. (1988) Nature 333:667-669; and Alderson et al. (1992) J. Immunol. 149:1252-1257.
In vitro studies with various types of cells have revealed that there are two mechanisms involved in the production of soluble receptors and cell surface antigens. One involves translation from alternatively spliced mRNAs lacking transmembrane and cytoplasmic regions, which is responsible for the production of soluble IL4R, IL-5R, IL-7R, IL-9R, G-CSF-R, and GM-CSF-R. Rose-John and Heinrich (1994); and Colotta et al. (1993). The other mechanism involves proteolytic cleavage of the intact membrane receptors and antigens, known as shedding. Proteolysis appears to be involved in the production of soluble LNGF-R, TNF-R, CD27, CD30, IL-1R, IL-6R, TGFβ-R, PDGF-R, and CD14 (Id.).
Matrix metalloproteinases (MMPs) are a family of enzymes that includes interstitial collagenase (MMP-1), 72 kDa and 92 kDa gelatinases (MMP-2 and MMP-9), stromelysins 1, 2 and 3, neutrophil collagenase, metalloelastase, matrilysin, and gelatinase A. These enzymes are secreted by cells within tissues and by infiltrating inflammatory cells. Collectively, they are capable of degrading most of the proteins in the extracellular matrix (ECM).
MMPs display different substrate specificities yet have several properties in common. They are all zinc-containing enzymes that require calcium for activity. They are secreted as zymogens and activated in situ, usually by release of an inhibitory N-terminal pro-piece containing a single cysteine residue. The attached pro-piece is believed to coordinate with the zinc in the active site of the proteinase, thereby suppressing the proteolytic activity. Activation may be accompanied by additional proteolytic cleavages that can generate active enzymes of lower molecular weights. All members of the MMP family have a short conserved region consisting of the HEXGH motif that provides two Zn-coordinating histidine residues and a glutamic acid residue that is considered part of the catalytic site. With few exceptions, MMPs also contain a hemopexin/vitronectin domain. The function of the hemopexin domain is unknown. For review see Ray and Stetter-Stevenson (1994) Eur. Respir. J. 7:2062-2072.
A variety of studies have indicated that MMPs are involved in tumor invasion and metastasis. A number of methods have been utilized to assess the presence of MMPs in human tumor tissues and serum from cancer patients. Positive correlations have been found between MMP expression and tumor invasion and metastasis in vitro, as well as in in vivo animal models. Matrisian et al. (1991) Am. J. Med. Sci. 302:157-162; Sato et al. (1992) Oncogene 7:77-83; Lyons et al. (1991) Biochemistry 30:1449-1456; Levy et al. (1991) Cancer Res. 51:439-444; Bonfil et al. (1989) J. Natl. Cancer Inst. 81:587-594; Sreenath et al. (1992) Cancer Res. 52:4942-4947; and Powell et al. (1993) Cancer Res. 53:415-422. MMPs have been associated with the malignant phenotype in a wide variety of human tissues, including lung, prostate, stomach, colon, breast, ovaries and thyroid, as well as squamous carcinoma of the head and neck. Matrisian et al. (1991); Sato et al. (1992); Levy et al. (1991); and Lyons et al. (1991). To date, the proposed role of MMPs in cancer has been limited to tissue remodeling in invasion and metastasis.
The MMPs are inhibited by members of the family of tissue inhibitors of metalloproteinases (TIMPs, e.g., TIMP-1, TIMP-2, and TIMP-3), which bind at the active site and block access to substrate. Matrix remodeling, which occurs during various normal and pathological processes depends on a critical balance between activated MMPs and inhibiting TIMPs. For reviews of MMPs and their inhibitors see Alexander and Werb (1991), In: Cell Biology of Extracellular Matrix, ed. Hay, Plenum Press, New York, pp. 205-302; Murphy et al. (1991) Br. J. Rheumatol. 30:25-31; Woessner (1991) FASEB J. 5:2145-2154; Matrisian (1992) Bioessays 14:455-463; Birkedal-Hansen et al. (1993) Crit. Rev. Oral Biol. and Med. 4:197-250; and Denhardt et al. (1993) J. Pharmacol. Ther. 59:329-341.
Recent studies suggest that metalloproteases may be involved in the cleavage of both TNF-Rs, LNGF-R, IL-6R, pro-TNF-α, VCAM-1, and CD30 and are thereby responsible for the production of the soluble forms. Crowe et al. (1995) J. Exp. Med. 181:1205-1210; Mullberg et al. (1995) J. Immunol. 155:5198-5205; Bjomberg et al. (1995) Scand. J. Immunol. 42:418-424; DiStefano et al. (1993) J. Neurosci. 13:2405-2414; Mohler et al. (1994) Nature 370:218-220; Gearing et al. (1994) Nature 370:555-557; McGeehan et al. (1994) Nature 370:558-561; Leca et al. (1995) J. Immunol. 154:1069-1077; and Hansen et al. (1995) Int. J. Cancer (1995) 63:750-756. Interestingly, a MMP is suggested to be responsible for the cleavage of pro-TNF-α. Gearing et al. (1994); and Gearing et al. (1995) J. Leukoc. Biol. 57:774-777. In addition, levels of serum matrix metalloproteinase 1 and 3 in rheumatoid arthritis patients were reduced following anti-TNF antibody therapy. Brennan et al. (1997) Br. J. Rheumatology 36:643-50. Anti-TNF antibodies have also been used to suppress fever, inflammation and the acute-phase response in juvenile chronic arthritis and rheumatoid arthritis cases, and to reverse endotoxin shock in rats. Elliott et al. (1997) Br. J. Rheumatology 36:589-93; Maini et al. (1997) Apmis 105:257-63; and Boillot et al. (1997) Crit. Care Medicine 25:504-11. One MMP inhibitor, GM-6001, prevents the release of TNF both in vitro and in vivo. Solorzano et al. (1997) Shock 7:427-31.
A number of MMP inhibitors have been described and the use thereof has also been suggested for treating various pathologic indications, including: angiogenesis; wound healing; gum disease; skin disorders; keratoconus; inflammatory conditions; rheumatoid arthritis; cancer; corneal and skin ulcers; cardiovascular disease; central nervous system disorders; and diabetes. U.S. Pat. Nos. 5,268,384 and 5,270,326; PCT publications WO 94/22309, WO 95/09913, WO 90/11287, WO 90/14363; EP patents 211 077, 623 676; and Naito et al. (1994) Int. J. Cancer 58:730-735; Watson et al. (1995) Cancer Res. 55:3629-3633; Davies et al. (1993) Cancer Res. 53:2087-2091; Brown (1995) Advan. Enzyme Regul. 35:293-301; Sledge et al. (1995) J. Natl. Cancer Inst. 87:1546-1550; Conway et al (1995) J. Exp. Med. 182:449-457; and Docherty et al. (1992) TibTech 10:200-207. However, the ability to treat arthritis by inhibiting matrix metalloproteases has been questioned. Vincenti et al. (1994) Arth. & Rheum. 37:1115-1126.
Both soluble p55 and p75 TNF-R do not appear to be generated from processed mRNA, since only full length receptor mRNA has been detected in human cells in vitro. Gatanaga et al. (1991). Carboxyl-terminal sequencing of the human soluble p55 TNF-R indicates that a cleavage site may exist between Asn 172 and Val 173. Gullberg et al. (1992) Eur. J. Cell. Biol. 58:307-312. This evidence is supported by the finding that human TNF-R with the mutation at Asn 172 and Val 173 was not released as effectively as native TNF-R on COS-1 cells transduced with cDNA of human TNF-R. Gullberg et al. (1992). The cytoplasmic portion of TNF-R does not appear to play an important role in releasing the soluble receptor forms from transduced COS-1 cells. COS-1 cells release sTNF-R even when transduced with cDNA of human p55 TNF-R which expresses only the extracellular domain but not the cytoplasmic domain. (Id.) sTNF-R shedding is not affected by dexamethasone, gold sodium thiomalate, or prostaglandin E2. Seitz et al. (1997) J. Rheumatology 24:1471-6. Collectively, these data support the concept that human sTNF-R are produced by proteolytic cleavage of membrane TNF-R protein.
It would be useful to purify and characterize the protease that cleaves TNF-R and results in the generation of sTNF-R. The purification and characterization of this proteinase will reveal the role of sTNF-R in host-tumor interactions and in treatment of pathogenic conditions mediated or exacerbated by TNF. Although claims have been made to the TRRE (EP 657 536), analysis of the claimed protein sequences given by BLAST Protein Sequence Homology Search reveals that they match the TNF-R. This may be due to the use of a TNF-R affinity column during protein purification. Thus, the nature of the protein and its DNA and AA sequences have not yet been elucidated.
In spite of numerous advances in medical research, cancer remains the second leading cause of death in the United States. In the industrialized nations, roughly one in five persons will die of cancer. Traditional modes of clinical care, such as surgical resection, radiotherapy and chemotherapy, have significant failure rates, especially for solid tumors. Failure occurs either because the initial tumor is unresponsive, or because of recurrence due to regrowth at the original site and/or metastases. Even in cancers such as breast cancer where the mortality rate has decreased, successful intervention relies on early detection of the cancerous cells. The etiology, diagnosis and ablation of cancer remain a central focus for medical research and development.
Neoplasia resulting in benign tumors can usually be completely cured by removing the mass surgically. If a tumor becomes malignant, as manifested by invasion of surrounding tissue, it becomes much more difficult to eradicate. Once a malignant tumor metastasizes, it is much less likely to be eradicated.
The three major cancers, in terms of morbidity and mortality, are colon, breast and lung. New surgical procedures offer an increased survival rate for colon cancer. Improved screening methods increase the detection of breast cancer, allowing earlier, less aggressive therapy. Lung cancer remains largely refractory to treatment.
Excluding basal cell carcinoma, there are over one million new cases of cancer per year in the United States alone, and cancer accounts for over one half million deaths per year in this country. In the world as a whole, the five most common cancers are those of lung, stomach, breast, colon/rectum, and uterine cervix, and the total number of new cases per year is over 6 million. Only about half the number of people who develop cancer die of it.
Melanoma is one of the human diseases for which there is an acute need of new therapeutic modalities. It is a particularly aggressive form of skin cancer, and occurs in increased frequency in individuals with regular unguarded sun exposure. In the early disease phases, melanoma is characterized by proliferation at the dermal-epidermal junction, which soon invades adjacent tissue and metastasizes widely. Once it has metastasized, it is often impossible to extirpate and is consequently fatal. Worldwide, 70,000 patients are diagnosed annually with melanoma and it is responsible for 25,000 reported deaths each year. The American Cancer Society projects that by the year 2000, 1 out of every 75 Americans will be diagnosed with melanoma.
Neuroblastoma is a highly malignant tumor occurring during infancy and early childhood. Except for Wilm's tumor, it is the most common retroperitoneal tumor in children. This tumor metastasizes early, with widespread involvement of lymph nodes, liver, bone, lung, and marrow. While the primary tumor is resolvable by resection, the recurrence rate is high.
Small cell lung cancer is the most malignant and fastest growing form of lung cancer and accounts for 20-25% of new cases of lung cancer. Approximately 60,000 cases are diagnosed in the U.S. every year. The primary tumor is generally responsive to chemotherapy, but is followed by wide-spread metastasis. The median survival time at diagnosis is approximately 1 year, with a 5 year survival rate of 5-10%.
Breast cancer is one of the most common cancers and is the third leading cause of death from cancers in the United States with an annual incidence of about 182,000 new cases and nearly 50,000 deaths. In the industrial nations, approximately one in eight women can expect to develop breast cancer. The mortality rate for breast cancer has remained unchanged since 1930. It has increased an average of 0.2% per year, but decreased in women under 65 years of age by an average of 0.3% per year. Preliminary data suggest that breast cancer mortality is beginning to decrease, probably as a result of increased diagnoses of localized cancer and carcinoma in situ. See e.g., Marchant (1994) Contemporary Management of Breast Disease II: Breast Cancer, In: Obstetrics and Gynecology Clinics of North America 21:555-560; and Colditz (1993) Cancer Suppl. 71:1480-1489.
Non-Hodgkin's B cell lymphomas are cancers of the immune system that are expected to afflict approximately 225,000 patients in the United States in 1996. These cancers are diverse with respect to prognosis and treatment, and are generally classified into one of three grades. The median survival of the lowest grade is 6.6 years and the higher grade cancers have much lower life expectancy. Virtually all non-Hodgkin's B cell lymphomas are incurable. New diagnoses of non-Hodgkins lymphomas have increased approximately 7% annually over the past decade, with 52,700 new diagnoses estimated for 1996. The increase is due in part to the increasing prevalence of lymphomas in the AIDS patient population.
In spite of the difficulties, effective cures using anticancer drugs (alone or in combination with other treatments) have been devised for some formerly highly lethal cancers. Most notable among these are Hodgkin's lymphoma, testicular cancer, choriocarcinoma, and some leukemias and other cancers of childhood. For several of the more common cancers, early diagnosis, appropriate surgery or local radiotherapy enables a large proportion of patients to recover.
Current methods of cancer treatment are relatively non-selective. Surgery removes the diseased tissue, radiotherapy shrinks solid tumors and chemotherapy kills rapidly dividing cells. Chemotherapy, in particular, results in numerous side effects, in some cases severe enough to preclude the use of potentially effective drugs. Moreover, cancers often develop resistance to chemotherapeutic drugs.
Recently, a method of in situ treatment of cancers, particularly pancreas, has been shown to be efficacious. The method involves creating an mixed lymphocyte reaction (MLR) between the host (cancer patient's) peripheral blood lymphocytes and a donor's allogeneic lymphocytes and administering the MLR directly to the tumor. This method is described more fully, for example, in WO 93/20186 and JP 62096426. In the case of large solid tumors, administration of the MLR is preceded by resection of the tumor.
Like cancers, weight problems are also associated with TNF. TNF is linked to the three factors contributing to body weight control: intake, expenditure, and storage of energy. Administration of either TNF or IL-1, for example, induces a decrease in food intake. Rothwell (1993) Int. J. Obesity 17:S98-S101; Arbos et al. (1992) Mol. Cell. Biochem. 112:53-59; Fargeas et al. (1993) Gastroenterology 104:377-383; Plata-Salaman et al. (1994) Am. J. Physiol. 266:R1711-1715; Schwartz et al. (1995) Am. J. Physiol. 269:R949-957; and Oliff et al. (1987) Cell 50:555-563. Interestingly, TNF may have a key roles in both extremes of weight problems. Abnormalities in its activity may lead to obesity; changes in its production result in the opposite effect, cachexia. Argilés et al. (1997) FASEB J. 11:743-751.
Cachexia is pathological weight loss generally associated with anorexia, weakness, anemia, asthenia, and loss of body lipid stores and skeletal muscle protein. This state often accompanies burns, trauma, infection, and neoplastic diseases. Lawson et al. (1982) Annu. Rev. Nutr. 2:277-301; Argilés et al. (1988) Mol. Cell. Biochem. 81:3-17; and Ogiwara et al. (1994) J. Surg. Oncol. 57:129-133. TNF concentrations are elevated in many patients with cachexia. Scuderi et al. (1986) Lancet 2:1364-65; Grau et al. (1987) Science 237:1210-1212; and Waage et al. (1986) Scand. J. Immunol. 24:739-743. TNF inhibits collagen alpha I gene expression and wound healing in a murine model of cachexia. Buck et al. (1996) Am. J. Pathol. 149:195-204. In septicemia (the invasion of bacteria into the bloodstream), increased endotoxin concentrations may raise TNF levels, causing cachexia. Beutler et al. (1985) Science 229:869-871; Tracey et al. (1987) Nature 330:662-664; and Michie et al. (1988) New Engl. J. Med. 318:1481-1486. During cachexia, the loss of white adipose tissue is caused by the decreased activity of lipoprotein lipase (LPL); TNF lowers the activity of this enzyme. Price et al. (1986) Arch. Biochem. Biophys. 251:738-746; Cornelius et al. (1988) Biochem. J. 249:765-769; Fried et al. (1989) J. Lipid. Res. 30:1917-1923; Semb et al. (1987) J. Biol. Chem. 262:8390-8394; and Evans et al. (1988) Biochem. J. 256:1055-1058. Fat tissue loss is also associated with an increase in lipase activity and inhibition of glucose transport; TNF is also linked to both of these changes. Kawakami et al. (1987) J. Biochem. 331-338; Feingold et al. (1992) Endocrinology 130:10-16; and Hauner et al. (1995) Diabetologia 38:764-771. TNF mediates hypertriglyceridaemia associated with cachexia. Dessi et al. (1995) Br. J. Cancer 72:1138-43. TNF also participates in the protein wasting, loss of skeletal muscle and loss of nitrogen associated with cachexia. Costelli et al. (1993) J. Clin. Invest. 92:2783-2789; Flores et al. (1989) J. Clin. Invest. 83:1614-1622; Goodman (1991) Am. J. Physiol. 260:E727-730; Zamir et al. (1992) Arch. Surg. 127:170-174; Llovera et al. (1993) J. Natl. Cancer Inst. USA 85:1334-1339; and Garcia-Martinez et al. (1993) FEBS Lett. 323:211-214.
TNF has additional, related roles. It is involved in thermogenesis, particularly nonshivering thermogenesis in brown adipose tissue (BAT), which has an elevated level in cachexia. Nicholls (1983) Biosci. Rep. 3:431-441; Rothwell (1993) Int. J. Obesity 17:S98-S101; Bianchi et al. (1989) Horm. Metab. Res. 21:11; and Oudart et al. (1995) Can. J. Physiol. Pharmacol. 73:1625-1631. TNF has also been implicated in non-insulin-dependent (type II) diabetes. Hotamisligil et al. (1995) J. Clin. Invest. 95:2409-2415; Arner (1996) Diabetes Metab. 13:S85-S86; Spiegelman et al. (1993) Cell 73:625-627; Saghizadeh et al. (1996) J. Clin. Invest. 97:1111-16; and Hofmann et al. (1994) Endocrinology 134:264-270. These data help explain how TNF mediates the opposite effects of obesity and cachexia. TNF has functional similarities to those of leptin, which has been proposed to be an “adipostat.” Zhang et al. (1994) Nature 372:425432; Phillips et al. (1996) Nature Genet. 13:18-19; and Madej et al. (1995) FEBS Lett. 373:13-18. Like leptin, for example, TNF is expressed and secreted by adipocytes and can travel to the brain. TNF administration also results in an increase in circulating leptin concentrations. Grunfeld et al. (1996) J. Clin. Invest. 97:2152-57. It is possible to reconcile the participation of TNF in obesity and cachexia. TNF can be considered one of many signals coming from adipose tissue that participate in the feedback mechanism that informs the hypothalamic center about the state of the adipocyte energy depot. It probably counteracts excessive energy intake and is able to stimulate thermogenesis either directly or by increasing sympathetic activity. TNF released by adipose tissue will also stimulate lipolysis, decrease LPL activity, decrease the expression of the glucose transporter GLUT4, and inhibit lipogenesis in the adipocyte, thus contributing to the maintenance (but not increased fat deposition) of the adipose tissue mass. In cachexia, however, the situation is different. A high production of TNF by activated macrophages (as a result of a tumor or an infection) also contributes to anorexia, increased thermogenesis, and adipose tissue dissolution. However, it represents a pathological state where there is an excess of the molecules that inform the brain that adipose tissue needs dissolution. The two situations can thus be reconciled: in cachexia there is a pathological overproduction of TNF; in obesity, the physiological action of TNF as a signal to control food intake and energy expenditure is impaired. Argilés et al. (1997). FASEB J. 11:743-751.